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This invention relates to the profiling of containers using an ultrasonic liquid level sensor to detect a series of data points that are processed to determine information about the containers, such as container type, whether the container is capped, and, if the container is not capped, the liquid level in the containers.
This application is related to the following U.S. patent applications, having the indicated titles, which are commonly-assigned to the Bayer Corporation of Tarrytown, N.Y. and are incorporated by reference herein:
Utility patent applications for Robotics for Transporting Containers and Objects within an Automated Analytical Instrument and Service Tool for Servicing Robotics, Ser. No.
Utility patent applications for Robotics for Transporting Containers and Objects within an Automated Analytical Instrument and Service Tool for Servicing Robotics Ser. No. 09/115,080, filed concurrently herewith (abandoned); Automatic Handler for Feeding Containers Into and Out of An Analytical Instrument (xe2x80x9cSample Handlerxe2x80x9d), Ser. No. 09/115,391, filed concurrently herewith (U.S. Pat No. 6,227,053); Sample Tube Rack, Ser. No. 09/097,790, filed Jun. 15, 1998 (U.S. Pat. No. 6,065,617); Reagent Package, Ser. No. 08/985,759(U.S. Pat. No. 6,043,097), filed Dec. 5, 1997; Diluent Package, Ser. No. 29/088,045, filed May 14, 1998; Stat Shuttle Adapter and Transport Device, Ser. No. 09/113,640 (U.S. Pat. No. 6,074,617), filed Jul. 10, 1998; Automatic Decapper, Ser. No. 09/115,777, filed concurrently herewith (U.S. Pat. No. 6,257,091); and Cup Handling Subsystem for an Automated Clinical Chemistry Analyzer System Ser. No. 09/099,738, filed Jun. 18, 1998 (U.S. Pat. No. 6,254,312).
A variety of different types and sizes of test tubes and inserts (such as Ezee Nest(copyright) tubes that are inserted into ordinary Vacutainer(copyright) test tubes or sample cups that are inserted into Microtainer(copyright) holders), generically xe2x80x9ccontainersxe2x80x9d (or xe2x80x9cvesselsxe2x80x9d), are currently in use in laboratories and hospitals throughout the world. However, there are only a few such containers that comprise the majority of containers in use. These include the Vacutainer(copyright) test tubes and Microtainer(copyright) holders, both manufactured by the Becton-Dickinson Corporation, test tubes from Sarstedt of Germany, and the two types of inserts mentioned above: Ezee Nest(copyright) inserts and Microtainer(copyright) holders. Other test tubes are manufactured by Braun of Germany, Meditech, Inc. of Bel Air, Maryland, and Greiner, among others. The below discussion refers to the Vacutainer(copyright) and Sarstedt test tubes and the inserts but would apply equally to other test tubes and other containers as long as sufficient information is provided to the workstation software for the system to identify the containers and distinguish them from other containers.
The Vacutainer(copyright) test tubes are available in 4 sizes, 13 mm (diameter)xc3x9775 mm (height), 13 mmxc3x97100 mm, 16 mmxc3x9775 mm, and 16 mmxc3x97100 mm. All of these Vacutainer(copyright) test tubes may be capped with a rubber stopper or a rubber Hemoguard(copyright) cap. The test tubes that are 75 mm in height may alternatively have an Ezee Nest(copyright) insert, which holds a small amount of a sample, inserted into the top of the Vacutainer(copyright) test tube to be supported by the lip of the test tube. The Sarstedt test tubes are available in two sizes: 16 mmxc3x9775 mm and 16 mmxc3x9792 mm and may be capped with unique twist-on caps. The other referenced test tubes likewise have unique features, such as size, that are sufficient to identify them.
Some of the various types of containers referred to above are shown in FIG. 1. The containers are numbered 1-19 and identified in the identification key on FIG. 1. The maximum height of each container is listed below the figure of that container. The listed height includes the height of the container plus any additional height due to the height of the cap or insert.
It is important to be able to process the different types of containers in an automated analytical instrument while requiring as little human intervention, such as data entry of information about the containers, as possible. It would therefore be useful to have an analytical instrument that dynamically determines the container type and liquid level in the container. Similarly, the instrument should also be able to detect capped test tubes in order to know which test tubes must be automatically decapped at an automatic decapping area of the instrument before further processing of the test tubes.
It is further desirable to maximize the throughput of the analytical instrument. One way to maximize throughput is to minimize the downward travel of a probe for aspirating liquid samples from the containers by maximizing the speed with which the probe may be lowered. The probe must enter the liquid slowly so as not to enter the liquid surface at a high velocity, which would perturb the hydraulic interface at the probe tip. If the liquid level in each container is known before the probe is lowered, the probe may be quickly lowered to slightly above the liquid level and a capacitive liquid level sensor on the tip of the probe may be used to lower the probe the additional small distance necessary to enter the sample. This speeds up the cycle time in which each sample is aspirated, as otherwise the probe would have to be lowered at a steady, slow rate until the probe determines the liquid level. To lower the probe more quickly requires a specific acceleration/deceleration motion profile determined by the location of the top surface of the liquid.
An ultrasonic sensor may be used to detect objects not in contact with the sensor. (FIG. 2) The ultrasonic sensor comprises a transducer 21 with a piezoelectric tip mounted in a sensor holder 20. Transducer 21 alternates between operating as a transmitter and receiver. When operating as a transmitter, an electrical pulse is applied to transducer 21, causing transducer 21 to ring at a particular ultrasonic frequency, which is in the range of approximately 50 kHz to 2 MHz. Transducer 21 rings freely until it eventually stops ringing. The ringing transmits an ultrasonic burst, represented by arrow 23, for a length of time that is dependent on the pulse width applied to transducer 21 and the size of transducer 21. The ultrasonic burst has a greater amplitude when initially generated and then attenuates over time. (FIG. 4) The burst propagates through air toward a targeted surface, such as surface 22, and, when it strikes the targeted surface, at least a portion of the wave which is not absorbed by the surface, if any, is reflected back toward sensor 21 as one or more echoes 24. The sensor is able to detect the echoes after it has finished ringing and is switched to a receive mode.
The ultrasonic burst propagates as a cone-shaped wave. Referring to FIG. 3, where a first surface 25 has an aperture 26, the burst will impinge upon the first surface 25 and pass through the aperture 26 to impinge on a second lower surface 29, if any. The burst is reflected back from the first, closer surface 25 as a first echo 27 and from the second, farther surface 29 as a second echo 28, which arrives at sensor 21 after the first echo 27. The time it takes for each ultrasonic burst to travel from sensor 21 and to return back to sensor 21 as one or more echoes is captured in memory. Software, known to those skilled in the art and typically included by the sensor manufacturer in a printed wire assembly (referred to below as a data acquisition board) which is designed to operate with the sensor, then converts the time measurements to measurements of the distance which the ultrasonic bursts have traveled using the known speed of sound (which equals 331.36 m/sec at ambient temperature).
An ultrasonic sensor may be used in a variety of applications to take measurements over a wide range of distances. They may be used as short range sensors to take measurements as close as a few centimeters away from the sensor or as long range sensors to take measurements as far away as a few meters. Ultrasonic sensors have typically been used in applications such as detecting and identifying solid objects, measuring the shape and orientation of a workpiece, detecting possible collisions between objects to avoid the collisions, room surveillance, flow measurement, and determining a type of material by measuring the absorption of sound.
Ultrasonic liquid level sensing is a known process that uses an analog ultrasonic sensor to measure the level of liquid in a container without physically contacting the liquid. One such sensor that may be used for ultrasonic liquid level sensing is described in U.S. Pat. No. 5,507,178 assigned to Cosense, Inc. of Hauppauge, N.Y. Cosense also manufactures an ultrasonic micro measurement system ML-102, which may be used for liquid level sensing. Ultrasonic sensors are better suited for liquid level sensing in narrow containers than optical sensors because they are at most nominally affected by dust, may be used over a wide range of distances, are inexpensive, and light does not interfere with the measurements. The Cosense sensor has been used by the Becton-Dickinson Corporation for determining the level of liquid in Micro pipette trays that are statically placed underneath the sensor.
It is also known in the prior art that information regarding the profile of vehicles passing a toll booth may be collected using an ultrasonic low frequency broad beam long range sensor, which is far less precise than an ultrasonic liquid level sensor, to determine the volume and types of vehicles, such as whether it is a car or truck, passing a particular toll booth. The sensor takes a number of readings, collecting data points to create a profile of the vehicles. Obviously, the precise model or manufacturer of the vehicle is unimportant in this situation and an imprecise profile containing data points which are not processed further to obtain precise measurements may be used to provide the required information.
It is therefore an object of this invention to provide a method of using an ultrasonic sensor that transmits an ultrasonic beam focused downward on a moving rack of containers to profile the rack and containers and thereby determine information about them, which may include the type and size of the container, whether the container is capped, and, if the container is not capped, the liquid level in the containers.
The present invention is directed to a method of profiling one or more containers in a rack using the ultrasonic sensor. The rack is transported within a sensing range of the sensor, in particular, by transporting the rack with a rack transport mechanism, such as a cross-feed or shuttle, under the ultrasonic sensor at a slew speed, while the ultrasonic sensor transmits a plurality of ultrasonic bursts toward the rack. As the sensor may be used to profile relatively small containers, the sensor is preferably operated as a short range sensor with bursts emitted at a frequency of 1 MHz. The sensor detects echoes generated by the ultrasonic bursts striking the rack and the containers as the rack is transported past the sensor and these echoes are detected. The first and second echoes generated by each of the bursts are captured and processed to profile the containers. Using the detected echoes, a processor generates data points indicating the distance the echoes traveled in a single direction before being reflected back to the ultrasonic sensor. These data points are saved in a memory device associated with the ultrasonic sensor and are processed to profile the container.